Brake or clutch lining

ABSTRACT

The present invention relates to brakes or clutches having the frictional surfaces thereof boronized on one or both of the braking or clutching surfaces.

1 1 June 12, 1973 References Cited UNITED STATES PATENTS BRAKE OR CLUTCHLINING Inventors:

[75] Helmut Kunst,

Osterholz-Scharmbeck; Heinrich 1,966,130 7/1934 Wasels Altena both ofGermany 3,282,746 Zlotek 6i a]. 1,746,924 2/1930 Bendix [73] Assignees:Institute fur Harterei-Teehnlk, 2,925,896 2/ 1960 Jaeschke Lesumer;Heinrich Wasels, Altena 3,306,741 2/1967 Lallemant....

(Westphalia) Klusenstrasse, both OTHER PUBLICATIONS of Germany Chem.Abstracts Vol. 68: 107l50e (1968).

[ Filed: 11, 1971 Chem. Abstracts V0]. 69: 60988n (1968).

[21] Appl. No.2 123,222

Primary Examiner-Ralph S. Kendall Att0rneyFrancis M. Crawford [30]Foreign Application Priority Data Feb. 13, 1970Germany...................

[57] ABSTRACT The present invention relates to brakes or clutches havingthe frictional surfaces thereof boronized on one or both of the brakingor clutching surfaces.

4 Claims, 2 Drawing Figures m nimum 2191s INVENTOR. HELMUT KUNST BRAKE RCLUTCH LINING The present invention relates to brakes or clutches havingat least two friction surfaces, that is, two surfaces which when pressedupon each other restrict the movement of the moving parts.

Numerous attempts have been made in the past to construct brakes andclutches wherein the braking and clutching surfaces exhibited improvedproperties with respect in particular to mechanical and thermal stressesand strains without at the same time unduly increasing the cost ofconstruction and repair. Among such, attention might be called to GermanPat. No. 1,026,644 which describes the coating of the breaking surfacesof brake drums with a light metal, such as molybdenum, by spraying orprecipitation from the vapor phase. Such methods have been subject tovarious disadvantages not present in the improved method which is thesubject of the present invention.

According to the present invention, the frictional surfaces of brakes orclutches are constructed in a manner such that they are able to takemuch heavier loads, have a longer useful life and can be produced moreeconomically. This improvement is effected by coating at least one ofthe frictional surfaces of the brake or clutch with a boride layer,preferably by boronizing by conventional methods.

The boronizing of metal surfaces is well known being frequently resortedto when it is desired to produce hard surfaces. It was surprising todiscover, however, that such boronized metal surfaces were highlyeffective as friction surfaces in brakes and clutches, resulting fromthe unexpected discovery that such surfaces have an unusually highfrictional coefficient. This is especially when boronized iron metalsurfaces are used. It was found upon investigation that this surprisingproperty is apparently due to the special crystal structure of the ironboride layer formed upon the boronized iron metal surface, the boridecrystals being formed on the supporting iron metal surface in a mannerso that the individual iron boride crystals will protrude from thesurface to different heights. An uneven surface having protusions andrecesses is thus formed, with the result that the frictional coefficientof the surface is materially increased.

It has further been discovered that the individual boride crystalspenetrate the supporting iron metal in the form of teeth and are thusanchored therein, giving an increased advantage to the use of boronizediron surfaces as frictional surfaces for brakes and clutches. Stillanother advantage in the use of frictional surfaces prepared in thismanner results from the fact that boride layers which have penetrated bydiffusion are quite hard, resistant to thermal stresses, as well as toabrasion, thus making them particularly desirable for use as frictionalsurfaces for brake and clutch surfaces.

In producing the improved frictional surfaces of the present inventionthe boride layer may be produced upon brake or clutch parts producedfrom castable metal alloys, such as malleable cast iron, gray cast ironor other such alloys, as well as from sintered metals. Among the metalswhich are particularly suitable may be mentioned the thermally refinedlow alloy or even unalloyed steels, which have good thermal conductanceand hence are able to conduct away heat rapidly from the surfaces asformed. In this connection it might be noted that the coefficient ofthermal expansion of the boride layer is so similar to that of the lowalloy or unalloyed steels that even when highly heated splitting off ofthe boride layer due to differences in expansion does not take place toany particular degree.

To further illustrate our improved invention reference is made to theattached drawings.

FIG. 1 shows parts of a brake drum, to illustrate one possibleapplication of our invention.

FIG. 2 shows, on an enlarged scale, a section of the friction surfaceillustrated in FIG. 1.

It is understood that the invention illustrated by the above FIGS. canbe applied to all types of brakes or clutches having friction surfaces.

In FIG. 1 showing a brake drum section 10 containing a brake shoe 11located inside of the brake drum.

The faces of the brake drum 10 and brake shoe 11,

which face each other, can be pressed upon each other along the brakingsurfaces 12 and 13. At least one of these braking surfaces 12 and 13 isproduced in accordance with the present invention, that is, is coatedwith a boride layer 14. As a typical example, the braking surface of thebraking drum 10 is coated with a boride layer 14, whereas the brake shoe11 carries a conventional type brake liner 15 to provide the brakingsurface 13.

The boride layer 14, shownin enlarged scale in FIG. 2, is produced bydiffusion upon the supporting material, that is, the part 16 of thebrake or clutch, in a manner so that the boride crystals 17 are producedvertical to the braking face. These boride crystals 17 are anchored intothe supporting material by tooth-like ends 18, that is, anchored withsuch teeth inside the brake or clutch portion 16, so that the boridelayer 14 is effectively bonded to the supporting material.

FIG. 2 also illustrates the fact that the boride crystals 17 do not forma smooth surface in which all of the crystals are flush with each other.Instead, they form the braking surface 12 in which the boride crystalsare present in staggered heights with size differences of the order ofabout 2 microns. It is this difference in surface structure which givesthe unusually favorable coefficient of friction and facilitates theremoval of heat formed by the braking action, due to the increasedsurface.

The supporting material 16 of the brake or clutch is preferably a metalwhich can be cast in molds, such as malleable cast iron, gray iron,spheroidal-graphite iron castings, sintered metals or similar materials.Particularly suitable are the thermally refined low alloyed or unalloyedsteels, which permit excellent removal of heat by conduction.

In the modification illustrated by FIG. 1 the brake drum 10 may consistof any suitable material, such as aluminum. Into the brake drum 10 isinserted a supporting ringl7, by shrinking or other suitable means. Thisarea of the supporting ring 17 which faces the brake shoe 11 serves asthe braking face 12 and is provided with the boride layer 14. Thesupporting ring 17 can be any of the materials listed above as suitablesupporting materials for the boride layer.

What is claimed is:

1. Brake or clutch containing two friction faces comprising a ferrousmetal base, which can be pressed against each other, at least one ofsaid friction faces being coated with a boron layer applied by diffusionboronizing, the boron being formed on the supporting metal surface inthe form of teeth anchored therein and anchored into the supportingmaterial by tooth-like ends whereby said boride crystals are effectivelybonded to said frictional surface.

4. Brake or clutch according to claim 1 wherein said boron layer is inthe form of boride crystals produced vertical to the frictional surfaceand are in staggered heights with size differences of the order of about2 microns.

1. Brake or clutch containing two friction faces comprising a ferrousmetal base, which can be pressed against each other, at least one ofsaid friction faces being coated with a boron layer applied by diffusionboronizing, the boron being formed on the supporting metal surface inthe form of teeth anchored therein and which protrude from the surfaceof said supporting metal to different heights.
 2. Brake or clutchaccording to claiM 1 wherein said boron layer is applied to a supportingmetal selected from the group consisting of malleable cast iron, grayiron, spheroidal-graphite iron castings, steels, low alloyed steels andsintered steels.
 3. Brake or clutch according to claim 1 wherein saidboron layer is in the form of boride crystals produced vertical to thefrictional surface, and said crystals being anchored into the supportingmaterial by tooth-like ends whereby said boride crystals are effectivelybonded to said frictional surface.
 4. Brake or clutch according to claim1 wherein said boron layer is in the form of boride crystals producedvertical to the frictional surface and are in staggered heights withsize differences of the order of about 2 microns.